Add 21/42 and 42/90
21/42 + 42/90 is 29/30.
Steps for adding fractions
- Find the least common denominator or LCM of the two denominators:
LCM of 42 and 90 is 630
Next, find the equivalent fraction of both fractional numbers with denominator 630 - For the 1st fraction, since 42 × 15 = 630,
21/42 = 21 × 15/42 × 15 = 315/630 - Likewise, for the 2nd fraction, since 90 × 7 = 630,
42/90 = 42 × 7/90 × 7 = 294/630 - Add the two like fractions:
315/630 + 294/630 = 315 + 294/630 = 609/630 - 609/630 simplified gives 29/30
- So, 21/42 + 42/90 = 29/30
MathStep (Works offline)
Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad
Related: 21/42+84/90 21/84+42/90 63/42+42/90